1. Field of the Invention
This invention relates generally to catheters and in particular to cholangiogram catheters which are retained within hollow anatomical structures such as cystic ducts by the fastening of a sealing or clamping member around the duct that exerts a substantial compressive force upon the catheter.
2. Description of the Related Art
Cholangiography generally involves the insertion of a catheter into an anatomical duct such as the cystic duct followed by the introduction of a radio-opaque or other contrast medium into the ductal system, for the purpose of radiographic or endoscopic examination of a targeted body organ such as the gallbladder. During the course of cholangiography, a primary concern is that the catheter not slip from the position in which it has been placed in the duct, which may occur by reason of a back pressure against the catheter that can be built up from the forcing of the contrast medium forwardly into the duct. Another major concern is the avoidance of leakage of contrast medium backwards through the duct past the catheter head.
In the past, various techniques of retaining the catheter in place within the cystic duct and sealing fluid flow around the catheter have included simple ligature, Javid clamp, and a loosely applied hemoclip. In addition, cholangiogram catheters have included heads with abruptly-defined flash shoulders thereon to aid in forming a seal against leakage. A more recently developed technique has been to tightly fasten an endoscopic surgical clip around an outer wall section of the cystic duct behind the shoulder of the catheter, which clip compresses the outer wall section of the duct and causes the inner wall of the duct to snugly grip the catheter in the zone behind its shoulder, thereby inhibiting slippage of the catheter from its position within the duct and preventing leakage of contrast medium backwards past the head of the catheter. Such surgical clips are usually bent or otherwise fastened around the duct by means of a substantial clamping force exerted by a special endoscopic clip-applying instrument.
Because of the size and structure of this type of clip-applying instrument, as well as the relatively confined location in which it is used, it is often very difficult and highly user-dependent to be able to apply just enough clamping pressure on the clip to fasten it sufficiently tight so as to assure retention of the catheter within the duct and to provide an adequate seal between the duct and catheter, but without collapsing or occluding the catheter. As a result, there exists a serious problem of inadvertent occlusion or collapse of the catheter within the duct produced by an overtightening of the clip. Such occlusion or collapse of the catheter can impair or defeat its use and effectiveness for performing the cholangiography and any subsequent endoscopic procedure. Accordingly, there is a recognized need in the art for a cholangiogram catheter which is resistant to deformation produced by an excessive clamping force when a sealing member is tightly fastened around the duct. The present invention is directed toward preventing inadvertent occlusion or collapse of the catheter by providing a headed catheter with a substantially inflexible internal support tube that defines an uncollapsible section of the catheter which cannot easily bend or be compressed along any part of such section.